This invention relates to a curable protective coating for a silicone gel. More particularly, this invention relates to a fluorocarbon dispersion that cures to yield an elastomeric fluorocarbon coating that acts as a barrier to fuel adsorption by the silicone gel.
Commercially available silicone gels are designed to be soft, have low modulus, and have a tacky surface. Silicone gels are useful in protecting electrical and electronic devices. Exposing a silicone gel based on a polydimethylsiloxane polymer to a fuel is known in the art to cause extremely high adsorption and high volume swell.
One method of reducing fuel adsorption uses gels based on fluorosilicone polymers. For example, U.S. Pat. No. 4,719,275 issued on Jan. 13, 1988, to Benditt et al. discloses fluoroalkylpolysiloxane gels that are resistant to hydrocarbon fuels. However, these gels can still adsorb enough fuel to cause swell that will adversely affect the performance of some electronic devices. Another method of reducing fuel adsorption is by coating silicone gels with fluorosilicone elastomers. For example, U.S. Pat. No. 4,465,805 issued on Aug. 14, 1984, to Blizzard et al. discloses fluorosilicone elastomers that are resistant to hydrocarbon liquids and are useful as coatings. However, gels coated with fluorosilicone elastomers can still adsorb enough fuel to cause swell that will adversely affect electronic device performance.
U.S. Pat. 5,368,315 issued on Nov. 29, 1994, to Viksne discloses a non-stick automotive gasket comprising a resilient material with a polymeric fluorocarbon coating. The coating is obtained using a dispersion of polymeric fluorocarbon particles in a silicone fluid. The resilient material absorbs the silicone fluid, leaving a coating of polymeric fluorocarbon on the surface of the resilient material. The fluorocarbon prevents the resilient material of the gasket from sticking to engine parts and prevents liquid lubricants and coolants from leaking.
U.S. Pat. No. 5,551,707 issued on Sep. 3, 1996, to Pauley et al. discloses a composite seal that includes a layer of plastic material, such as a fluorocarbon, sandwiched between layers of elastomeric material, such as a fluorosilicone. The layers are held together by an ethylene vinyl alcohol adhesive. The fluorocarbon layer has a lower permeability to the fluid being sealed than one of the layers of fluorosilicone material.
U.S. Pat. No. 4,395,462 issued on Jul. 26, 1983, to Polmanteer discloses a fluorocarbon elastomer used as a coating for cured and peroxide-curable silicone rubber compositions. The fluorocarbon elastomer reduces gas permeability and imparts abrasion resistance to the silicone rubber substrate. However, Polmanteer does not disclose the fluorocarbon elastomer as a coating for silicone gels; and furthermore, Polmanteer does not disclose use of the fluorocarbon elastomer to reduce swelling of the substrate on which it is coated in the presence of a fuel.
One object of the present invention is to provide a silicone gel product comprising a silicone gel with a fluorocarbon elastomer on the surface thereof. The fluorocarbon elastomer reduces swelling of the silicone gel in the presence of a fuel. A further object of the present invention is to provide a method of producing the silicone gel product.